I have never grown this plant from a leaf. Usually you have to start with the whole leaf, intact all the way to the base, for that to work in this family.
These plants are great looking for the first season (especially when they flower in the summer) but then they tend to start looking a little unkempt as the stem extends and they start to grow sideways. That seems to be the natural habit of the plant. It is normal for them to have stem without living leaves below the first year's flower. The flowers are terminal (so the plant has to branch afterwards).
The flowers are also pretty powerful bug magnets.
If you want to propagate the plant down the road you can try beheading it when it's going strong. Root that cutting separately and the mother plant may very likely sprout branches. I have one of these in a pot where the growth center died off earlier this year and it now has about a dozen new heads.
